While reading this chapter for the last four days it was difficult for me to interpret as there is no concrete moral lesson to teach or a behaviour to adopt as it is in almost every chapter in the Daodejing. My chapter was more symbolic and poetic as it thought that it was a metaphor showing the valley as a woman, but when I read again and again and asked for some help, I saw the message behind all of the symbolic elements of this chapter and that the valley was a person 's mind even if there are mountains or hills, they will always go and the valley will still be empty. The mountains and the hills means the things in life, good or bad. All of these things will fade and go down to the empty valley.
The line "The gateway of the mysterious female, Is called the root of heaven and earth" means that this female is the one that is producing everything. "When I drop it all away, all that is left is nothing—the mysterious female. In letting go, I come closer to the root of heaven and earth. "
The "letting go" part of this chapter relates to the non-action which is as the daoists say, the only way to return to the Dao and to the original self is by letting go. By stopping to try so much, everything will fall into place.
"Chapter 6 Commentary." Center Tao, centertao.org/essays/tao-te-ching/dc-lau/chapter-6-commentary/. Accessed 20 september 2019.